Deficits in working memory (WM) and cognitive control processes have been reported in post-traumatic stress disorder (PTSD), in addition to clinical symptoms such as hypervigilance, re-experiencing, and avoidance of trauma reminders. Given the uncontrollable nature of intrusive memories, an important question is whether PTSD is associated with altered control of interference in WM. Some studies also suggest that episodic memory shows a material-specific dissociation in PTSD, with greater impairments in verbal memory and relative sparing of nonverbal memory. It is unclear whether this dissociation applies to WM, as no studies have used identical task parameters across material. Here we tested 29 combat Veterans with PTSD and 29 age-matched control Veterans on a recent probes WM task with words and visual patterns in separate blocks. Participants studied four-item sets, followed by a probe stimulus that had been presented in the previous set (recent probe) or not (nonrecent probe). Participants with PTSD made more errors than controls, and this decrement was similar for verbal and visual stimuli. Proactive interference from items recently presented, but no longer relevant, was not significantly different in the PTSD group and showed no relationship to re-experiencing symptom severity. These results demonstrate that PTSD is not reliably associated with increased intrusions of irrelevant representations into WM when non-emotional stimuli are used. Future studies that use trauma-related material may provide insight into the flashbacks and intrusive thoughts that plague those with PTSD.

Speaking is an action that requires control, for example, to prevent interference from distracting or competing information present in the speaker’s environment. Control over task performance is thought to depend on the lateral prefrontal cortex (PFC). However, the neuroimaging literature does not show a consistent relation between left PFC and interference control in word production. Here, we examined the role of left PFC in interference control in word production by testing six patients with lesions to left PFC (centred around the ventrolateral PFC) on a control-demanding task. Patients and age-matched controls named pictures presented along with distractor words, inducing within-trial interference effects. We varied the degree of competing information from distractors to increase the need for interference control. Distractors were semantically related, phonologically related, unrelated to the picture name, or neutral (XXX). Both groups showed lexical interference (slower responses with unrelated than neutral distractors), reflecting naming difficulty in the presence of competing linguistic information. Relative to controls, all six left PFC patients had larger lexical interference effects. By contrast, patients did not show a consistent semantic interference effect (reflecting difficulty in selecting amongst semantic competitors) whereas the controls did. This suggests different control mechanisms may be engaged in semantic compared to lexical interference resolution in this paradigm. Finally, phonological facilitation (faster responses with phonological than unrelated distractors) was larger in patients than in controls. These findings suggest that the lateral PFC is a necessary structure in providing control over lexical interference in word production, possibly through an early attentional blocking mechanism. By contrast, the left PFC does not seem critical in semantic interference resolution in the picture-word interference paradigm.

The error-related negativity (ERN) is a neuroelectric signature of performance monitoring during speeded response time tasks. Previous studies indicate that individuals with anxiety disorders show ERN enhancements that correlate with the degree of clinical symptomology. Less is known about the error monitoring system in post-traumatic stress disorder (PTSD). PTSD is characterized by impairments in the regulation of fear and other emotional responses, as well as deficits in maintaining cognitive control. Here, combat Veterans with PTSD were compared to control Veterans in two different versions of the flanker task (n=13 or 14 per group). Replicating and extending previous findings, PTSD patients showed an intact ERN in both experiments. In addition, task performance and error compensation behavior were intact. Finally, ERN amplitude showed no relationship with self-reported PTSD, depression, or post-concussive symptoms. These results suggest that error monitoring represents a relative strength in PTSD that can dissociate from cognitive control functions that are impaired, such as response inhibition and sustained attention. A healthy awareness of errors in external actions could be leveraged to improve interoceptive awareness of emotional state. The results could have positive implications for PTSD treatments that rely on self-monitoring abilities, such as neurofeedback and mindfulness training.

We welcome our new post-doc, Dr. Matt Schalles, to the lab. Matt recently completed his Ph.D. in Cognitive Science at UCSD under the guidance of Dr. Jaime Pineda. Dr. Schalles is also Adjunct Psychology Faculty at Holy Names University.

VA-funded project to study the effects of post-traumatic stress disorder and traumatic brain injury on executive control of cognition and emotion. Multidisciplinary research environment for neuropsychological and event-related potential (ERP) studies of the neural organization and dynamic interplay of distributed regions that regulate responses to cognitive and affective conflict. Opportunities for collaborative research in structural and functional MRI with other investigators at the Martinez VA. The lab is affiliated with the Department of Neurology at University of California, Davis.

Ph.D. in Neuroscience, Psychology, Cognitive Science, Neurobiology or a related field required. EEG research experience strongly preferred. MATLAB programming skills a bonus. Initial appointment is for 2 years, with the possibility of renewal. Available now, but start date flexible.